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Power Circuit Breaker Selection Tables - GE AKD-10 Application Manual

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Power circuit breaker selection tables

Table 25.1 Transformer forced cooled ratings
Self-cooled
Transformer type
Liquid filled: 65° C rise
750-2000
2500-5000
Liquid filled: 55/65° C rise
750-2000
2500-5000
Ventilated dry
750-2500
Cast coil
500-2500
3000-5000
Table 25.2 208 volts, three phase
Transformer
rating 3-phase Max short-circuit
Full load
kVA and
MVA available
continuous
impedance
from primary
current
(amperes) Œ Ž
percent
system
50
100
300
150
4.5%
250
500
750
Unlimited
50
100
500
150
4.5%
250
500
750
Unlimited
50
100
750
150
Ž (2915)
5.75%
250
500
750
Unlimited
50
100
1000
150
Ž (3886)
5.75%
250
500
750
Unlimited
50
100
1500
150
5.75%
250
500
Ž (5830)
750
Unlimited
ΠWith transformer operating on base temperature rise, without fans. Larger frame
size main breaker may be required when dual temperature rise for forced cooled
transformers are used.
 Minimum impedance.
Ž Maximum forced cooled rating indicated in parentheses.
L = Long-time delay trip (overload tripping)
S = Short-time delay trip (selective fault tripping)
I = Instantaneous trip (high fault current fast tripping)
kVA
% increase with fans
15%
25%
15% (fans) + 12% (65° C)
25% (fans) + 12% (65° C)
33%
40%
25%
Short-circuit rating sym current (A)
Transformer
100%
alone
Motor load
16300
17300
17700
833
18000
1700
18300
18300
18500
25200
27800
28700
1388
29500
2800
30200
30400
30800
28700
32000
2082
33300
34400
4200
35300
35600
36200
35800
41100
2776
43300
45100
5600
46700
47200
48300
47600
57400
61700
4164
65600
8300
68800
70000
72400
Main
Fully rated or
selective
Selective
Fully rated
arrangement
LI
LS
LS
Selectively
coordinated
arrangements
Distribution or motor control center
Long-time inst.
or long-time
Long-time
short-time Œ
Combined
short-time
18000
19000
19400
19700
WPS-16
WPS-08
20000
20000
20200
28000
WPS-08
30600
31500
32300
WPS-16
WPH-08
33000
33200
33600
32900
36200
37500
38600
WPS-32
WPH-08
39500
39800
40400
41400
WPH-08
46700
48900
50700
WPS-32
WPX-08
52300
52800
53900
55900
WPX-08
65700
70000
73900
WPS-50
WPH-32
77100
78300
80700
Feeder circuit breakers
Zone
selective
Fully rated
LI
LSI
LI
Long-time
short-time
Long-time
inst.
inst.
WPS-08
WPS-08
WPS-08
WPS-08
WPS-08
WPS-08
WPS-08
WPS-08
WPH-08
WPH-08
WPX-08
WPX-08
WPX-08
WPX-08
WPS-32
WPS-32
25

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